Heretofore, in an operation for installing an instrument panel module (cockpit module) prepared by assembling various components around a support member (steering support member), to a dash member or the like of a vehicle body, it has been known to detachably attach two holding brackets, respectively, to opposite ends of the support member in such a manner that each of the holding brackets is disposed to be exposed beyond a front door opening edge of the vehicle body in a vehicle width direction when the instrument panel module is installed to the dash member of the vehicle body, and install the instrument panel module to the vehicle body while holding the holdable portion from an outside thereof in the vehicle width direction by the installation jig, as disclosed in the following Patent Literature.